Position detection with frequency smoothing

ABSTRACT

The invention relates to a method for calculating a position of a mobile communications equipment. In order to obtain a more accurate position information of the mobile communications equipment, receiving physical communication channels within the mobile communications equipment, receiving first signal codes within said physical communication channels, measuring a signal phase of said first signal code within said mobile communications equipment, measuring a pseudodoppler frequency within said physical communications channels within said mobile communications equipment, reducing a noise level of said measured signal phase by using said pseudodoppler frequency, and calculating said position of said mobile communications equipment using at least said noise level reduced signal phase, is proposed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/821,126filed on Apr. 8, 2004 and claims domestic priority under 35 U.S.C. §120.

FIELD OF THE INVENTION

The invention relates to a method for calculating a position of a mobilecommunications equipment, in particular a mobile phone. The inventionfurther relates to a mobile communications equipment able to calculate aposition. The invention also relates to a system for calculating aposition of a mobile communications equipment as well as a module, acomputer program and a computer program product for calculating aposition of a mobile communications equipment.

BACKGROUND OF THE INVENTION

Position detection is a known method in third generation mobilecommunication. In particular for code division multiple access (CDMA)mobile stations (MS), position detection using Advanced Forward LinkTrilateration (AFLT) is known.

Advance Forward Link Trilateration is a geolocation technique utilizingthe time difference of arrival (TDOA) or a time of arrival (TOA) ofradio signals from the base stations measured by mobile stations.

To allow calculation of the position of mobile stations, in particular acode phase is detected. The code phase may be the fraction of the codeperiod that has elapsed since the latest code boundary. By using thecode phase, the time of arrival or the time difference of arrival can becalculated.

Cellular network-related wireless location methods can be subdividedinto three categories according to the mobile station and networkfunctionalities. These three categories are pure network-based methods,MS-assisted network-based methods, and MS-based network-assistedmethods.

For a pure network-based method, the network fulfills all thepositioning functionalities including location measuring and positioncalculations. An MS itself does not take any active part in the process.Obviously, these methods are applicable to legacy cellular phones.However, the network may require some modifications to accommodate awide range of hardware products.

The second category, MS-assisted network-based methods, consists ofmethods, which require at least some active participation from the MSs.An MS can take part in location measuring or doing some otherpositioning-dedicated tasks, while most of the positioningfunctionalities are still completed in the network. The role of an MS issolely to assist the network in positioning.

In MS-based network-assisted methods, the roles of the MSs and thecellular network are reversed in comparison to those in the secondcategory method. An MS makes location measurements and calculates itsown position. Thus, the role of the network is simply to assist MSs inlocation estimation. Methods of this type enable a denserposition-fixing rate.

The simplest method for locating a cellular phone is CELL-ID, which isbased on cell identification. An MS can be assigned a location if thecell in which the MS is located can be identified. Since this is aninherent feature of all cellular systems, minimal changes to existingsystems are needed. A cell only has to be associated with a location,such as by association with the coordinates of the base station of thiscell.

This method boasts the additional advantage that no calculations areneeded to obtain location information. Thus, the CELL-ID based method isfast and suitable for applications requiring high capacity. However, thedrawback is that accuracy depends directly on cell radius, which can bevery large, especially in rural areas.

To allow position detection, geological techniques like time differenceof arrival and time of arrival are known.

Applying these techniques requires that the number of measurements isadequate to make an accurate estimation of the mobile station location.For instance, it is required that at least three TDOA measurements areavailable for uniquely determining the MS position. However, theunderlying communication system is designed to reduce the interferenceby maintaining the transmission powers of the MSs and BSs at a minimumrequired level in order to accommodate more users. Consequently, onlywhen the MS is at the edge of a cell, may it obtain enough measurementsfor location estimation. This is known as the hearability problem.

The angle of arrival (AOA)-based location method is one of the oldestpositioning methods. Its early use began during the development ofradar, sonar, and antenna array techniques. By means of array signalprocessing techniques, the direction of an MS with respect to BSs can bemeasured at BSs. Thus, the MS is at the intersection of the linesderived from AOA measurements. The accuracy of the AOA method isdependent on the distances between the MS to be located and the antennaarrays at BSs. The further the MS is from the antenna arrays, the largeris the positioning uncertainty. Non-line-of-sight (NLOS) signalpropagation is a significant source of inaccuracy. When NLOS componentsexist, AOA measurements will be distorted, thus resulting in degradedpositioning accuracy.

The measurements required in Time of Arrival (TOA) methods are theabsolute signal transmission times between MS and BSs that areequivalent to MS-BS distances. The MS is located at the intersection ofseveral circles, of which the centres are the BSs used, and the radiiare the measured MS-BS distances. At least three TOA measurements arerequired to uniquely determine the 2-D position of an MS.

TOA wireless location methods require that all base stations (BS) beprecisely synchronized to each other and that the MS to be located besynchronized to the network as well. For this reason, TOA positioning isfeasible only in fully synchronized networks; for example, in IS-95 CDMAsystems.

The measurements in Time Difference of Arrival (TDOA) methods arerelative signal transmission times, which are equivalent to distancedifferences. A TDOA measurement defines a hyperbola with two BSs as thefoci. At least three hyperbolae are needed for unique MS positiondetermination.

A TDOA method requires that all base stations involved be synchronized.This can be done either by synchronizing all BSs physically, or bybringing all BSs to a common reference time by measuring timedifferences between BSs. MSs do not need to be synchronized since the MSclock bias is the same with respect to all BSs and differencing any twoTOA measurements will cancel out the MS clock bias. It may also bepossible to provide the BSs with a time reference from a satellite basedpositioning signal, such as GPS.

In a CDMA System, a pilot phase signal is continuously transmitted. Thissignal allows mobile stations to detect the presence of CDMA channelsand provides timing information for demodulation. According to mobilecommunication standard, the pilot signal is a DS spread spectrum signal.The spread function is a zero Walsh function. The signal is furthermodulated by a pseudo noise (PN) sequence of a particular base station.The pseudo noise sequences of different base stations only differ in anoffset, which is a multiple of 64 pseudo noise chips.

In particular, there are 64 physical channels in the forward link of anIS-95 CDMA cellular system; these are distinguished by the 64 orthogonalWalsh functions, which serve as digital carriers. These physicalchannels form four types of logical channels.

First, the pilot channel is identified by Walsh function zero. Itcontinuously broadcasts a known signal to provide the MSs a robust time,frequency, and phase reference for demodulation in other channels.

The pilot channel possesses dominant transmission power. Approximately15-20% of the maximum transmission power of a BS is dedicated to thepilot channel to ensure the visibility of the pilot signal over thecoverage area. This also makes pilot signals more easily acquired fromneighboring cells as well. The pilot signal is a known continuousbroadcasting signal. It enables an MS to keep locked on the pilot PseudoNoise (PN) code. All BSs transmit the same PN sequence but withdifferent offsets. This makes it easier in the search process of areceiver to acquire TDOA measurements.

The process of generating a pilot signal provides a zero Walsh functionwith a chip rate of 1.2288 Mcps (mega chips per second). It is firstmodulated by the pilot baseband “data”. Then, this intermediate signalis separated into an I-component and a Q-component to further modulatethe I-channel PN sequence and the Q-channel PN sequence. Wave shaping,amplification, and RF carrier modulation are finally conducted togenerate the actual signal transmitted to MSs.

The Walsh code is one type of orthogonal code. It is used in IS-95 CDMAsystems to separate different physical channels. Both the I-channel PNsequence and the Q-channel PN sequence are maximal length sequencesgenerated by 15-stage shift registers and lengthened by the insertion ofone chip per period in a specific location in the sequences. Thus, thesequence length is in chips. Each base station is distinguished by adifferent phase offset in both the I-channel and the Q-channel PNsequences. The offset is a multiple of 64 PN chips, which yields 512possible 64-chip offsets. At a rate of 1.2288 Mcps, the I-sequence andQ-sequence repeat every 26.66 ms, or 75 times every 2 seconds.

The synchronization channel is identified by a Walsh function, and is acontinuously broadcasting channel. It provides MSs with BS timinginformation, cell site identification number, and other information forsynchronization.

In addition, there can be up to seven paging channels. A paging channelcontains paging messages and conveys other control messages from the BSsto the MSs.

Eventually, there are at least 55 traffic channels. They carry userinformation. They also carry control messages using “blank and burst”,which is a time multiplexing technique used on traffic channels to sendoverhead signaling or (optionally) secondary traffic in which a frame ofprimary digital voice data is blanked, i.e., not transmitted to allowthe overhead or secondary traffic to be transmitted at a 9600 bit/secondrate. In the blank-and-burst format, a frame or frames of primarydigital voice data are suppressed or not transmitted to make timeavailable to send signaling traffic. The digital voice frames are lost.However, the degradation of the recovered analog voice is minimalprovided not too many frames are blanked consecutively. Typically, thetransmitter controllers wait for a less-than-full-rate Vocoder frame inwhich signaling traffic can be multiplexed with voice traffic withoutthe loss of any voice bits.

Multiplexing signaling with voice in less-than-full-rate frames iscalled dim and burst, which is a time multiplexing technique used ontraffic channels to send overhead signaling or (optionally) secondarytraffic in which a less-than-full-rate frame of primary digital voicedata and overhead or (optionally) secondary traffic data are combinedand transmitted at a 9600 bit/second rate.

To allow location estimation, a method called forward link location isknown. Reception on forward link location is performed coherently. Tomaintain coherence, the MS searches for and locks onto a pilot pseudonoise (PN) sequence. Every base station sector broadcasts the pilot PNsequence with a unique known offset, as previously described. The basestations are synchronized, allowing the MS to identify the signaloriginating from a particular BS sector.

A common IS-95 mobile terminal has four rake receiver fingers, three ofwhich are used to receive an incoming signal and one to search formultipath signals and handover candidates. During operation, theterminal keeps track of the strongest pilot channel in its vicinity.When requested by the BS through a pilot measurement request order(PMRO), the BS will report all pilot signals it receives above a giventhreshold. The message sent back to the BS includes the magnitude ofeach pilot, relative to the offset of the base station transmitting thepilot signal.

The pilot signal may be used within the BS as phase reference. Knowingthe PN offsets of the pilots transmitted from nearby BSs it is possibleto construct TDOA estimates for the BS. As long as the MS is able todetect at least three pilot signals from three different BSs, thelocation estimation may be possible.

The main problems in location estimation using these methods aresynchronization errors in the BSs. These errors result from poor PNresolution and multipath or non-line-of-sight propagation of thereceived signals.

In particular the specifications 3GGP2 C.S0022-0, v1.0, “LocationService (position determination service)”, and 3GPP2 C.S0036-0, v.0,“Recommended Minimum Performance Specifications for C.S0022-0 SpreadSpectrum Mobile Stations” describe methods allowing code divisionmultiple access (CDMA) systems to calculate positions of mobileequipment. Depending on where the position calculation is performed, themethod may either be mobile station based or mobile station assisted. Ina mobile station based solution, the position may be calculated withinthe mobile phone itself. In the mobile station assisted case, a positionmay be calculated in a network server, in particular in a positiondetermination entity. The position determination entity may use for itsposition calculation information provided by the mobile station, inparticular phase and time measurements reported by the mobile station.

To allow calculation of a position using a time of arrival or a timedifference of arrival method, at least three different pilot phasesignals and pilot phase measurements should be provided. The pilot phasemeasurements are carried out within the mobile stations.

For position calculation within the mobile station, assistance data fromthe network is required. This assistance data may include theco-ordinates of the reference and neighboring base stations togetherwith their time corrections.

A drawback of known AFLT position measurements using pilot phasemeasurements is that the pilot phase signal is subject to noise. Thenoise level causes the pilot phase signal to be disturbed, thusdeteriorating the measured pilot phase.

SUMMARY OF THE INVENTION

The invention tries to improve the position calculation by measuring asignal phase of said first signal code within said mobile communicationsequipment, measuring a carrier signal within said physicalcommunications channels within said mobile communications equipment,reducing a noise level of said measured signal phase by using saidcarrier signal, and calculating said position of said mobilecommunications equipment using at least said noise level reduced signalphase.

The mobile communications equipment according to the invention may be amobile station such as a mobile phone.

According to embodiments, the invention provides using pseudodopplermeasurements for smoothing a code phase measurement in particular in anadvanced forward link trilateration environment. The method forsmoothing the measured signal phase as such is already known for globalpositioning signal receivers for carrier smoothing, in particular from“High-Precision GPS Navigation with Emphasis on Carrier-Phase AmbiguityResolution”, Lachapelle, et al., Marine Geodesy, Volume 15, pp. 253-269,1992, Taylor&Francis.

Pseudodoppler frequency may be understood as the measured Dopplerfrequency shift received from the communication signal, such as a CDMAsignal, received from a base station. Since the transmitter (Basestation) and receiver (mobile station) clocks are not synchronized andare subject to drifts, it is referred to as pseudodoppler.

By reducing the noise level of the pilot phase measurement, the qualityof position calculation will become more accurate. The smoothed pilotphase measurements will also be more robust against multipathpropagation phenomena or other channel impurities.

Carrier smoothing may probably not allow improving position detection.If there are not enough measurements or if the geometry of the basestations is not favorable for position calculation, pseudodopplermeasurements probably will not change the situation. However, it isproposed that pseudodoppler measurements are used in improving thequality of pilot phase measurements by reducing the noise of the pilotphase measurements. The noise may be induced by thermal noise,interferences, multipath, etc., which may be reduced by filtering thepilot phase measurements with pseudodoppler frequency.

For calculating said signal phase, a pilot channel may be used. A pilotchannel may be an unmodulated, direct-sequence spread spectrum signaltransmitted by a CDMA base station or a mobile station. A pilot channelprovides a phase reference for coherent demodulation and may provide ameans for signal strengths comparison between base stations fordetermining when to hand-off. A pilot phase offset may be the timedifference measured at the mobile station between the earliest arrivinguseable multipath component of a pilot and the mobile station systemtime reference.

To obtain the pseudodoppler frequency it is proposed that the phase ofsaid first signal code phase is tracked and said pseudodoppler frequencyis obtained from a carrier and/or phase tracking loop. According toanother embodiment the pseudodoppler frequency is obtained from matchedfilter outputs within said mobile communications equipment.

According to yet another embodiment the pseudodoppler frequency isobtained from accumulated carrier phase measurements from a carrierphase tracking loop. Accumulated carrier phase measurement is obtainedby integrating the output of the carrier phase tracking loop for aperiod of time, typically for the time between two code phasemeasurements (measurement interval). Accumulated carrier phase providesby far the most accurate estimate of the average Doppler frequencybetween two measurement instances if carrier phase lock has beenmaintained during the accumulation time without cycle slips. AverageDoppler frequency (pseudodoppler) can be calculated by dividing theaccumulated carrier phase by the accumulation time.

According to an embodiment, said physical communication channels aretransmitted from ground based base stations.

To allow calculating the position within the mobile network, it isproposed that said measured signal phase is transmitted from said mobilecommunications equipment to a base station.

To allow smoothing of the measured pilot phase within the mobilecommunications network, it is proposed that said measured pseudodopplerfrequency is transmitted from said mobile communications equipment tosaid base station.

Providing all available and measured information from the mobile stationto the base station allows calculating said position within anunderlying communications network, or even within a server remotelyattached to said network, such as delivering the data to the server viathe Internet.

To calculate the position based on the distance of a mobile station, itis possible to use a time of arrival calculation principle, as proposedin the CDMA protocol.

It is also possible to use a time difference of arrival calculationprinciple.

To assist the mobile station in calculating the position, it is proposedthat at least position information of said base station is transmittedfrom said base station to said mobile communications equipment.Furthermore, time corrections of the base stations may be transmitted.

One possible signal for phase measurement may be a pilot signal code, asproposed in the CDMA protocol.

To facilitate position detection, it is proposed that said base stationand said mobile equipment utilize a code division multiple accesscommunication protocol. Within this protocol, advanced forward linktrilateration is already described.

A hybrid position calculation may facilitate different methods forposition estimation. This may be combining position estimation fromGlobal Navigation Satellite Systems, such as, GPS, Galileo, GLONASS GNSSand position estimation from AFLT measurements. Also any othercombination of AFLT measurements with any position estimation usingcellular network measurements, Wireless Local Area Network (WLAN),and/or BlueTooth network measurements are possible. Other cellularnetwork measurements may be for example, round-trip time measurement,RX-level, Cell Identity, sector information, etc.

The invention will be described in greater detail in the followingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first flowchart;

FIG. 2 shows a second flowchart;

FIG. 3 shows a system for position detection; and

FIG. 4 shows an inventive mobile station.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a flowchart of messages exchanged between a mobilestation 2 and base station 4. Depicted are only messages between onebase station 4 and one mobile station 2, however, to allow positioncalculation, at least three base stations 4 have to provide signals toone mobile station 2.

Base station 4 provides mobile station 2 with pilot signals 8. The pilotsignals 8 are transmitted from base station 4 to mobile station 2 infrequent intervals. Together with pilot signal 8, further position andtiming information of base station 4 are transmitted to mobile station2. These may be the position of base station 4, possibly retrieved froma GPS signal received within the base station, as well as their timeshift. The base station 4 may be synchronized with other base stationsusing a GPS time reference received in the base stations.

Receiving the pilot signal 8 in mobile station 2 allows mobile station 2to calculate a pilot phase within step 12. This may be done by comparingthe phase of pilot signal 8 with a clock reference in the mobile station2. A clock reference in mobile station 2 corresponds to a clockreference in base station 4, thus a phase shift in pilot signal 8 may bedetected in mobile station 2. The pilot signal 8 is transmitted to saidmobile station 2 together with further signals 10, such assynchronization channel, paging channels, or traffic channels. Thesechannels may be utilized to obtain a pseudodoppler frequency.

The pilot phase measurement may be inaccurate due to signal noise.Therefore, mobile station 2 may obtain a pseudodoppler frequency. Thismay be done by tracking the phase of said first signal code phase andsaid pseudodoppler frequency is obtained from a carrier and/or phasetracking loop. The pseudodoppler frequency may also be obtained frommatched filter outputs within said mobile communications equipment.

The pseudodoppler frequency is acquired in step 14 within mobile station2. Using pilot phase and pseudodoppler frequency, the mobile station 2may calculate its position in step 16.

To reduce a noise level of said measured signal phase, it is proposedthat said noise level is reduced by smoothing the noise level byestimating the signal phase using said pseudodoppler frequency. Becausethe noise of the signal phase measurement is much larger compared to thepseudodoppler noise, it is advantageous to smooth the pilot phasemeasurement with the pseudodoppler measurement. The pseudodopplermeasurements are used in smoothing by estimating the carrier phasemeasurements with pseudodoppler frequency. This may be done by

ρ_(sm)(k)=ω_(sm)(k)×ρ_(AFLT)(k)+(1−ω_(sm)(k))×[ρ_(sm)(k−1)+f_(Dopp)(k)×ΔT _(AFLT)(k)]

whereω_(sm)(k)=smoothing gain,ρ_(AFLT)(k)=measured pilot phase at time k,ρ_(sm)(k)=smoothed pilot phase at time k,f_(Dopp)(k)=pseudodoppler frequency measurement at time kandΔT_(AFLT)(k)=time difference between two AFLT measurements at time k.

To allow providing a minimum smoothing weight, it is proposed that thesmoothing gain is reduced as

${\omega_{sm}(k)} = \left\{ \begin{matrix}{{{\omega_{sm}\left( {k - 1} \right)} - 0.01},} & {{{if}\mspace{14mu} {\omega_{sm}\left( {k - 1} \right)}} > \varpi_{sm}} \\{\varpi_{sm},} & {otherwise}\end{matrix} \right.$

where ω _(sm) is a threshold value for the minimum smoothing weight. Itis recommended that ω _(sm) will never be zero. Non-zero values willmake the smoother leaky, so that pilot phase smoothing will never purelybe based on pseudodoppler measurements. However, the above equations doonly represent one possible smoothing algorithm. Numerous otheralgorithms for smoothing the AFLT pilot phase measurements withpseudodoppler frequency are possible.

The calculated position may be provided to base station 4 with aposition message 18.

According to embodiments the pseudodoppler frequency is obtained fromaccumulated carrier phase measurements from a carrier phase trackingloop. Accumulated carrier phase measurement is obtained by integratingthe output of the carrier phase tracking loop for a period of time,typically for the time between two code phase measurements (measurementinterval). Accumulated carrier phase provides by far the most accurateestimate of the average Doppler frequency between two measurementinstances if carrier phase lock has been maintained during theaccumulation time without cycle slips. Average Doppler frequency(pseudodoppler) can be calculated by dividing the accumulated carrierphase by the accumulation time.

The depicted method may be carried out within frequent intervals or uponrequest. Depicted is only one interval.

A method for calculating a position of a mobile phone using advancedforward link trilateration, by receiving physical communication channelswith the mobile communications equipment, receiving first signal codeswithin physical communication channels, measuring a signal phase of saidfirst signal code within said mobile communications equipment, measuringa pseudodoppler frequency within said physical communications channelswithin said mobile communications equipment, smoothing said pilot signalphase by using said pseudodoppler frequency, and calculating saidposition using at least said smoothed pilot signal phase is providedaccording to embodiments.

FIG. 2 depicts position calculation within the mobile network. FIG. 2corresponds to FIG. 1 up to step 14. In mobile station 2 pilot phasemeasurements and pseudodoppler frequency are available. This informationis provided within a position message 20 to base station 4. Using thepilot phase information and the pseudodoppler frequency, base station 4calculates the position of mobile station 2 in step 22.

FIG. 3 depicts a system allowing position calculation with pilot phasesmoothing using pseudodoppler frequency. Depicted is mobile station 4 ina cellular network comprising base stations 2. Mobile station 4 receivesand transmits communication signals comprising physical communicationchannels to and from base stations 2, comprising pilot phase signals,synchronisation channels, paging channels and/or traffic channels. Thesechannels may carry position information and position measurementsinformation.

The signals, in particular CDMA signals, are doppler shifted, wherebythe time references of the BS 2 and the mobile station 4 are shifted,thus resulting in a pseudodoppler frequency.

Using the pseudodoppler frequency together with the pilot phase providedfrom the base station 2, mobile station 4 may calculate its position orprovide base station 2 with position information enabling base station 2to calculate the position of mobile station 4.

FIG. 4 depicts a mobile station 2 being able to calculate its positionusing a pilot phase measurement and a pseudodoppler frequency receivedfrom a CDMA base station. Reception means 24 allow receiving CDMAsignals. The CDMA signals may comprise a pilot signal. The CDMA signalsare provided to signal processors 28, 30. Signal processor 28 calculatesa pseudodoppler frequency from the CDMA signal.

The CDMA signals are also provided to signal processor 30. Within signalprocessor 30, a phase shift of the pilot signal is measured. The phaseof the pilot signal as well as the pseudodoppler frequency of the CDMAsignal are provided to calculation means 32. Within calculation means32, a noise level of said pilot phase is reduced by smoothing thissignal with the pseudodoppler frequency. The resulting signal is usedfor calculating a position of the mobile station 2 within positioncalculation means 34.

The signal processors 28, 30, the calculation means 32 and the positioncalculation means may be encapsulated within a module 36. This modulemay be provided in the mobile communication equipment if required forimproved position calculation.

Not depicted but also possible is to provide the information obtained insignal processors 28 and 30 via CDMA reception means 24 to a basestation. Within the base station the position of mobile station 2 isthen calculated.

According to embodiments a mobile communications equipment is providedcomprising reception means for receiving a physical communicationchannels, a first signal processor for measuring a signal phase of afirst signal code within said physical communication channels, a secondsignal processor for calculating a pseudodoppler frequency within saidphysical communications channels, and calculation means for calculatinga noise level reduced signal phase by using said pseudodopplerfrequency.

In addition, according to embodiments, a mobile communications equipmentis provided comprising reception means for receiving a physicalcommunication channels, a first signal processor for measuring a signalphase of a first signal code within said physical communicationchannels, a second signal processor for calculating a pseudodopplerfrequency within said physical communications channels, calculationmeans for calculating a noise level reduced signal phase by using saidpseudodoppler frequency, and position calculation means for calculatingsaid position using at least said noise level reduced signal phase.

In addition, a system for calculating a position of a mobilecommunications equipment is provided comprising in particular a mobilephone, and at least one ground based base station providing physicalcommunication channels comprising a first signal code, at least onemobile communications equipment, wherein said mobile communicationsequipment comprises a first signal processor for measuring a signalphase of a first signal code within said physical communicationchannels, a second signal processor for calculating a pseudodopplerfrequency within said physical communications channels, and calculationmeans for calculating a noise level reduced signal phase by using saidpseudodoppler frequency, is another aspect of the invention.

A computer program and a computer program product for calculating aposition of a mobile communications equipment, operable to cause aprocessor of a mobile communication equipment, as depicted in FIG. 4 toreceive physical communication channels within the mobile communicationsequipment, receive first signal codes within said physical communicationchannels, measure a signal phase of said first signal code within saidmobile communications equipment, measure a pseudodoppler frequencywithin said physical communications channels within said mobilecommunications equipment, and reduce a noise level of said measuredsignal phase by using said pseudodoppler frequency, is another aspect ofthe invention.

The invention allows a more accurate position detection of a mobilestation by smoothing a detected phase signal using a pseudodopplerfrequency of a CDMA signal.

1. A method, comprising: receiving signals from physical communicationchannels in a mobile communication device, said signals including afirst signal code and a carrier signal, measuring a signal phase of saidfirst signal code, calculating a frequency shift of said carrier signal,reducing a noise level of said measured signal phase by using saidfrequency shift, and calculating a position of said mobile communicationdevice using at least said noise level reduced signal phase.
 2. Themethod of claim 1, wherein said signal phase is a signal code phase. 3.The method of claim 2, wherein reducing the noise level of the measuredsignal code phase by using said frequency shift comprises filtering saidmeasured signal code phase with said frequency shift.
 4. The method ofclaim 1, wherein said calculated frequency shift is a pseudodopplerfrequency.
 5. The method of claim 1, wherein said frequency shift isobtained from an accumulated carrier phase measurement.
 6. The method ofclaim 3, wherein said filtering is done by carrier smoothing.
 7. Themethod of claim 2, wherein a threshold value for estimating said signalcode phase is defined.
 8. The method of claim 2, wherein the signal codephase of said first signal code is tracked and said frequency shift isobtained from a carrier and/or phase tracking loop.
 9. The method ofclaim 1, wherein said frequency shift is obtained from matched filteroutputs within said mobile communication device.
 10. The method of claim1, wherein said physical communication channels are transmitted fromground based base stations.
 11. The method of claim 1, wherein saidsignal phase is transmitted from said mobile communication device to abase station.
 12. The method of claim 11, wherein said measuredfrequency shift is transmitted from said mobile communication device tosaid base station.
 13. The method of claim 1, wherein said position iscalculated within an underlying communications network.
 14. The methodof claim 1, wherein said position is calculated using a time of arrivalcalculation principle.
 15. The method of claim 1, wherein said positionis calculated using a time difference of arrival calculation principle.16. The method of claim 1, wherein at least position information of abase station is transmitted from said base station to said mobilecommunication device.
 17. The method of claim 1, wherein said firstsignal code is a pilot signal code.
 18. The method of claim 1, wherein abase station and said mobile communication device communicate utilizinga code division multiple access communication protocol.
 19. The methodof claim 1, wherein said position is calculated using a hybrid positioncalculation.
 20. An apparatus, comprising: a receiver configured toreceive communication signals within physical communication channels, afirst signal processor configured to measure a signal phase of a firstsignal code received within said physical communication channels, asecond signal processor configured to calculate a frequency shift from acarrier signal received within said physical communications channels, acalculation device configured to calculate a noise level reduced signalphase by using said frequency shift, and a position calculation deviceconfigured to calculate a position of said mobile communication deviceusing at least said noise level reduced signal phase.
 21. The apparatusof claim 20, wherein said signal phase is a signal code phase andwherein said calculation device is further configured to calculate thenoise level reduced signal phase by filtering the measured signal codephase with said frequency shift.
 22. A system, comprising: at least onebase station configured to provide physical communication channels, andat least one mobile communication device, wherein said mobilecommunication device comprises: a receiver configured to receivecommunication signals within said physical communication channels, afirst signal processor configured to measure a signal phase of a firstsignal code received within said physical communication channels, asecond signal processor configured to calculate a frequency shift from acarrier signal received within said physical communications channels,and a calculation device configured to calculate a noise level reducedsignal phase by using said frequency shift, and wherein the systemfurther comprises: a position calculation device configured to calculatea position of said mobile communication device using at least said noiselevel reduced signal phase.
 23. The system of claim 22, wherein saidsignal phase is a signal code phase and wherein said positioncalculation device is further configured to calculating the noise levelreduced signal phase by filtering said measured signal code phase withsaid frequency shift.
 24. A computer program product, comprising acomputer-readable medium storing program codes thereon for use in amobile communication device, said program codes comprising: instructionsfor receiving signals from physical communication channels within themobile communication device, said signals including a first signal codeand a carrier signal, instructions for measuring a signal phase of saidfirst signal code, instructions for calculating a frequency shift fromthe carrier signal received from said physical communications channels,and instructions for reducing a noise level of said measured signalphase by using said frequency shift.
 25. The computer program product ofclaim 24, wherein said signal phase is a signal code phase and whereinthe instructions for reducing the noise level of said measured signalphase by using said frequency shift comprise: instructions for filteringsaid measured signal code phase with said frequency shift.
 26. A modulein communication with a receiver of a mobile communication devicecapable of receiving signals in communication channels, comprising: afirst signal processor configured to measure a signal phase of a firstsignal code received within said physical communication channels, asecond signal processor configured to calculate a frequency shift from acarrier signal received within said physical communications channels,and a calculation device configured to calculate a noise level reducedsignal phase by using said frequency shift.
 27. The module of claim 26,wherein said signal phase is a signal code phase and wherein saidcalculation device is further configured to calculate the noise levelreduced signal phase by filtering a measured signal code phase with saidfrequency shift.
 28. A mobile communication device, comprising: meansfor receiving communication signals in physical communication channels,means for measuring a signal phase of a first signal code receivedwithin said physical communication channels, means for calculating afrequency shift from a carrier signal received within said physicalcommunications channels, and means for calculating a noise level reducedsignal phase by using said frequency shift, and means for calculating aposition of said mobile communication device using at least said noisereduced signal phase.
 29. A mobile communication device, comprising:means for receiving communication signals in physical communicationchannels, means for measuring a signal phase of a first signal codereceived within said physical communication channels, means formeasuring a frequency shift from a carrier signal received within saidphysical communications channels, means for calculating a noise levelreduced signal phase by using said frequency shift, and means forcalculating a position of said mobile communication device using atleast said noise reduced signal phase, wherein said signal phase is asignal code phase, and wherein reducing said noise level of saidmeasured signal code phase by using said frequency shift comprisesfiltering said measured signal code phase with said frequency shift. 30.A module in communication with a receiver of a mobile communicationdevice capable of receiving signals in communication channels,comprising: a first signal processor for measuring a signal phase of afirst signal code received within said physical communication channels,a second signal processor for measuring a frequency shift from a carriersignal received within said physical communications channels, acalculation device for calculating a noise level reduced signal phase byusing said frequency shift, and a calculation device for calculating aposition of said mobile communication device using at least said noisereduced signal phase, wherein said signal phase is a signal code phase,and wherein reducing said noise level of said measured signal code phaseby using said frequency shift comprises filtering said measured signalcode phase with said frequency shift.